In practice, form tool cutters are conventionally provided with dovetail lower portions that fit into dovetail slots in suitable tool holders as shown, for example, in the U.S. Pat. No. 3,566,723 to Alfred C. Osborne dated Mar. 2, 1971. The dovetail slot usually extends entirely across the tool holder, and one side of the cutter dovetail is clampingly engaged by a plate that forms one side of the slot and is suitably detachably fastened to the holder as by screws or the like. When the screws are tightened, the dovetail portion of the cutting tool is clamped solidly between the clamping plate and the opposite side of the dovetail slot and, when the screws are loosened, the tool is released by the clamping plate for easy adjustment in the slot or for removal thereof for sharpening or replacement. In operation, the cutting tool is positioned in the dovetail slot with one end portion thereof projecting from the slot so that the cutting edge of the tool can be moved by the slide on which the tool holder is mounted into engagement with the work without interference from the holder.
Form tools are shaped in accordance with the configuration required by the particular job, and the cutter is sharpened by flat-grinding the working end of the cutter. As the cutter is ground away by successive sharpenings, it finally becomes so short that it can no longer be held adequately tightly by the clamping plate. When the cutting tool is new, it may extend substantially the full length of the dovetail slot so that the holding force exerted by the clamping plate is applied substantially uniformly against the entire length of the tool within the slot. However, as the cutting tool becomes progressively shorter in use, it finally reaches a point where the clamping plate no longer bears uniformly against the dovetail with the result that the tool shifts in the holder during a cutting operation. As a consequence, a defective part is produced which has to be scrapped. Alternatively, the cutter may simply break which of course ruins the cutter.
In a typical situation a new cutter may be 21/2" long. By the time it has been ground away to half its length, it is so short that it cannot be properly held in the cutter using a conventional side clamping plate as hereinabove described. When this happens, the cutter usually is simply thrown away. This represents a waste since the cutters are made of expensive tungsten carbide or high speed steel.